Whisky is one of the most diverse spirits in the world when it comes to flavour. From light, airy grain expressions to deeply peated, smoky, earthy drams, there’s a depth and breadth to drinking experiences like no other.
Yet when it comes to how whisky is made, there are remarkable similarities. Yes, small tweaks will have a huge impact on flavour. And yes, there are tips and tweaks we won’t cover here. But if you want to break down whisky production, you can slice it into four neat stages: grains and grain processing, fermentation, distillation, and maturation, blending and bottling.
How whisky is made in four steps
Different regions around the world will have slightly different whisky production methods. Some are defined in law. Even within American whiskeys, for example, there are different requirements for bourbons, ryes and single malts. This is a general guide, and we’ll discuss some of the most important variations as we go.
Ready? Grab a tasting glass and read on.
Grains and grain processing
Whisky has three basic raw materials: water, yeast and grain. The grains used will depend on the category of whisky, where it’s made and local laws, and intended flavour. The mix of grains used in a whisky’s recipe is known as a mash bill. Here’s a rough guide to commonly used grains:
- Single malt: 100% malted barley
- Grain whisky: any whole grain
- Blended Scotch is a mix of the two styles
- Malted barley, unmalted barley, other cereal grains
- Corn, rye, wheat and barley, depending on category and style
- Any whole grain, including quinoa, oats, buckwheat and millet
Once the grains have been selected, they will be milled, cooked (if relevant) and mashed, to make something akin to a porridge. Once drained, the whisky-maker is left with a sugary liquid ready for the next stage.
Fermentation
Different whisky-makers will use different types of yeast. Typically, and for high-volume producers, this will be a distiller’s yeast. Increasingly smaller scale, craft producers are experimenting with different types of yeast, including heritage strains and those used in brewing. These decisions will all impact flavour.
Once the yeast is chosen, it’s added to the sugary liquid. The subsequent fermentation can take place for a number of days depending on the type of yeast, ambient temperature, and the flavours the whisky-maker wants to develop at this stage.
The liquid left at the end of fermentation is called ‘wash’. It’s a bit like a beer, with a typical alcohol content of 8-10% ABV. Sometimes a whisky-maker will let the wash sit for a period of time so bacteria can develop, bringing with them more complex flavours.
Distillation
Once the wash is ready, it will be pumped into the stillhouse for distillation. At this stage, whisky-makers again have a number of choices. In distillation, it comes down to still type, shape and length of distillation run. Some of these may be determined by local laws, others will be very intentional based on what the intended final spirit is.
There are two main types of stills: pot and column stills. Pot stills are like large copper kettles and operate in a batch system. Pot stills are often used in pairs – a wash still for a first distillation run, a spirit still for the second. Some producers, especially in Ireland, will use pot stills three times.
As the liquid boils in a pot still, it will rise up the pot, out the top, down the lyne arm and into a condenser, where it turns back to liquid. The most volatile – most alcoholic – parts in the mixture will condense fastest. Over time, the less volatile – least alcoholic – parts of the mixture follow. This means that on the final (second or third) distillation run, a whisky-maker can choose when they want to ‘select’ the spirit.
The first part of the spirit, the ‘heads’, come off first. These will smell and taste very solventy, and won’t be captured for the spirit. Over time, when the spirit character changes, the whisky-maker will start to capture the spirit. This second is what will go on to become whisky – and it’s known as the ‘heart’. This will typically come off the still at 65-70% ABV.
Over time, the spirit will change again. It will become cheesy and plastic-like, and not suitable for the final spirit. The whisky-maker will stop capturing this section, known as the ‘tails’.
The heads and tails will be held separately and added back into a future final distillation run.
Column stills are tall, can be operated continuously, and feature a number of plates, which act a little bit like miniature pot still distillations. The heads and tails move up and down the still, through the plates, simultaneously. As long as there’s an equal amount of wash going in and spirit going out, the distillation process can run 24/7.
Column stills are much more flexible than pot stills. The ‘heart’ can be taken at any point on the still. Column stills are typically capable of producing much higher ABV spirits, too.
Tall pot stills create lighter spirit than shorter ones. Column stills can be used to make similar spirits to pot stills. And there are even hybrid stills which feature design elements of both. Producers in some categories are compelled to use certain stills, for example, single malt Scotch must be made in a column still. But for many, there’s a lot of flexibility. The possibilities in distillation are endless.
Maturation, blending and bottling
Depending on where a distillery is located, there will be specific rules around maturation and bottling. Whiskies sold in the EU and UK must be aged in oak for a minimum of three years. This rule doesn’t apply in the US, where you can buy very young spirits labelled as ‘whisky’.
But, if a whisky is to be matured, there are choices from the moment the spirit leaves the still. The vessel a spirit is aged in will have a profound impact on flavour. Over its maturation period, the liquid will be drawn in and out of a cask as it expands and contracts with time. Casks are watertight (we hope) but not air-tight, hence the movement and interaction between oak and spirit.
US and European oak barrels are generally used for ageing, although producers are experimenting with oak from elsewhere in search of different flavours. Most notably, Mizunara oak casks are coming to prominence, celebrated for the specific complex tasting notes they impart.
Barrel choice is tremendously important. New barrels will give a very specific type of intense flavour to a spirit. As will smaller casks. Previous contents will influence flavour too – for example, ex-bourbon barrels give a very different character than ex-Sherry butts. Bourbon casks give a creamy toastiness with sweet spices. Sherry butts will contribute big fruit, nutty notes.
Climate also plays a role. Casks maturing in warmer climates typically ‘age’ faster. Whiskies take their time in cooler climes. Compare five year old whiskies from India and Scotland if you want to explore this element.
Even the position a barrel holds in a warehouse – and the type of warehouse – will impact flavour. Heat rises, so the higher up a barrel is, the faster it will mature.
Whiskies can be aged for just a few years or for decades. Sometimes they will be ‘reracked’ into another cask type to bring in more flavour influences. For the duration of their maturation, they will be closely monitored. It is possible for a whisky to become ‘over-aged’. At that point, the oak influence is too much.
Once a whisky has come of age, the whisky-maker has more choices again. A single cask or single barrel release is just that, the liquid from one vessel bottled as it is. These releases can offer a very different and distinct drinking experience – because of all the facets involved in maturation, no two casks will ever taste the same.
More commonly, a whisky will be blended and vatted prior to bottling, even for single malt releases from one distillery. Here, a group of casks will be combined, or ‘married’, first.
For blended styles, where more than one category is combined, the blending process can be a complex one.
Whiskies will then be bottled. Very rarely this will be at natural colour and natural cask strength. More commonly it will be ‘proofed down’ with water to a desired ABV, and if permitted, caramel colour, or E150a, will be used to adjust colour.
Whisky making is a compelling mix of science and magic. How it’s made has captivated whisky lovers for centuries. And there’s always more to learn.